Antiglare coating and articles

ABSTRACT

The present invention relates to articles comprising an antiglare layer, coating compositions suitable for making antiglare layers, methods of making an antiglare article, and methods of making antiglare coating compositions. In some embodiments the article is a (e.g. illuminated) display article such as a touch screen. The antiglare layer comprises aggregate silica particle in a cured inorganic polymer matrix.

BACKGROUND

As described in U.S. Pat. No. 5,725,957, there are primarily two methodsof reducing glare associated with surfaces of glass substrates. Thefirst method involves depositing an “interference” coating stack on theglass substrate that controls glare by taking advantage of the opticalinterference within thin films. Such films usually have a thickness ofabout one-quarter or one-half the nominal wavelength of visible light,depending on the relative indexes of refraction of the coating andglass. The second method involves forming a light scattering, i.e.diffusing, means at the surface of the glass, usually either by alteringthe characteristics of the outermost surface of the glass substrate orvia a diffuser coating on the glass substrate.

Interference coatings reduce glare without reducing resolution. However,they are relatively expensive to deposit, requiring the use ofrelatively high cost vacuum deposition techniques such as sputtering andprecise manufacturing conditions, or very precise alkoxide solution dipcoating techniques, with subsequent drying and firing. Strict thicknesscontrol and uniformity are required.

In attempting to reduce glare by diffusion of light, one approach hasbeen to etch the outer surface of the glass substrate, or otherwisemodify the outer surface of a coating deposited on the glass substrate.There are numerous drawbacks in etching or otherwise modifying thesurface characteristics of a substrate or coated substrate. Etching bychemical means involves handling and storage of generally highlycorrosive compounds (e.g. hydrofluoric acid). Such compounds createprocessing and disposal problems in view of increasingly stringentenvironmental laws. Etching by non-chemical means, such as bysandblasting, necessitates additional and costly processing operations.In U.S. Pat. No. 5,725,957, a transparent substrate is spray coated witha precursor solution formed by dissolving a precursor of an inorganicmetal oxide in an organic solvent. As an alternative, another approachhas been to incorporate diverse materials (e.g. mixed oxides havingdifferent refractive indexes) into coating compositions.

Although various approaches of reducing glare have been described,industry would find advantage in new approaches for providing anantiglare surface.

SUMMARY OF THE INVENTION

In one aspect the invention relates to an article such as a touch screencomprising a glass substrate, an active element for detecting a touch onthe touch screen, and an antiglare layer. The antiglare layer comprisesaggregate silica particles in a cured inorganic polymer matrix whereinthe aggregates form surface structures ranging in size from 0.1micrometers to 2 micrometers. The active element may comprise atransparent conductive layer (e.g. comprised of transparent conductiveoxide) disposed between the glass substrate and the antiglare layer.

In some embodiments, the (e.g. touch screen) article preferablycomprises a silicon oxide layer disposed between the transparentconductive layer and the antiglare layer and/or a liquid crystal silanesurface layer.

The (e.g. touch screen) article typically has any one or combination ofthe following optical properties including a reflected haze of at least150, a reflectance of less than 10%, and a transmission of at least 80%.

The (e.g. touch screen) article typically has any one or combination ofthe following durability properties including a scratch resistance asdetermined by the Nanoscratch Test of at least 10 mN, a Taber AbrasionResistance test of at least 100 cycles, and a time to failure asdetermined by the Polishing Test of at least 2 hours for a 1 micrometerantiglare layer.

The silica particles typically have a mean particle size ranging fromabout 0.05 micrometers to about 0.15 micrometers.

The surface structures typically have a dimension of at least 0.20micrometers or 0.30 micrometers. The surface layer has a total surfacearea and the surface structures comprise at least 20%, at least 30% orat least 40% of the total surface area.

The cured inorganic polymer matrix is typically derived from anorganosilane usch as a silicon alkoxide. The cured organosilane istypically derived from a sol-gel process.

In other embodiments, the invention relates to a coating compositioncomprising an organosilane and flocculated silica particles ranging insize from 0.2 micrometers to 2 micrometers. The silica particles aretypically present in a concentration of less than 10 wt-%.

In another embodiment, the invention relates to a method of making anantiglare article with the coating composition.

In another embodiment, the invention relates to a method of making anantiglare coating composition comprising providing an inorganic polymerprecursor and colloidal silica particles having a mean particle sizeranging from 0.05 micrometers to 0.15 micrometers; and forming aninorganic polymer solution concurrently with flocculating colloidalsilica aggregates having a mean particle size of no greater than 2micrometers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three dimensional view of a touch panel having an antiglaresurface layer in accordance with the invention.

FIG. 2 depicts the particle size distribution of an illustrative coatingcomposition suitable to be employed for making an antiglare surfacelayer.

FIG. 3 is an illustrative antiglare surface at a magnification of 50×.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to articles comprising an antiglare (e.g.surface) layer, coating compositions suitable for making antiglarelayers, methods of making an antiglare article, and methods of makingantiglare coating compositions. In some embodiments the article is a(e.g. illuminated) display article such as a touch screen.

Various touch screens are known in the art, such as those described inU.S. Pat. Nos. 4,198,539; 4,293,734; and 4,371,746; incorporated hereinby reference. Touch screens typically comprise a (e.g. computer) touchsensitive panel such as commercially available from 3M Touch Systems,Inc., Methuen, Mass.

One exemplary display 10 of FIG. 1 includes touch panel 12 that includesan insulative substrate 14, such as glass, plastic or anothertransparent medium and active portion 15 on substrate 14. Active element15 for detecting a touch input typically includes a transparentconductive layer 16 deposited directly on substrate 14. Layer 16 istypically a doped tin oxide layer having a thickness of twenty to sixtynanometers and may be deposited by sputtering, vacuum deposition andother techniques known in the art. Conductive layer 16 may also includea conductive polymeric material or a conductive organic-inorganiccomposite. A conductive pattern, (not shown), is typically disposedabout the perimeter of conductive layer 16 to provide a uniform electricfield throughout conductive layer 16 in order to establish the point ofcontact between the display and a finger or stylus. Second conductivelayer 20 may optionally be provided to shield display 10 from noise thatmay result from the electric circuits of a display unit, (not shown), towhich display 10 may be attached and may similarly include a tin oxidelayer deposited in a similar manner as discussed with reference toconductive layer 16. The touch panel includes an antiglare layer 18 inaccordance with the invention.

In the article of the invention the antiglare layer may be present as asurface layer, such as depicted in FIG. 1. Alternatively, the antiglarelayer is disposed between the surface layer and the substrate (e.g. 14).The presence of layers above the antiglare layer does not detract fromthe structural features, the optical properties, nor the durabilityproperties of the antiglare layer as will subsequently be described.

The antiglare surface layer comprises aggregate silica particles in acured inorganic polymer matrix. The aggregate silica particles have amaximum dimension ranging in size from 0.1 micrometers to about 100micrometers. The aggregate silica particles preferably have a maximumdimension of at least 0.2 micrometers and more preferably at least 0.3micrometers. The discrete silica particles that form the aggregates aresubstantially smaller in size than the surface structures. As usedherein, an “aggregate” refers to at least two particles bonded together.The surface structures are comprised of one or more aggregate silicaparticles. Accordingly, the surface structures have a maximum dimensionranging from the size of a single aggregate to 70 micrometers andgreater.

Without intending to be bound by theory, by use of a cured inorganicpolymer matrix to bind the surface structures, the resulting antiglaresurface can advantageously provide a synergistic balance of antiglareoptical properties in combination with high levels of durability.Antiglare is typically characterized by a combination of opticalproperties. Among such optical properties, reflected haze andreflectance are usually most indicative of the antiglare property. Thereflected haze is typically at least 150 and more typically at least200. The reflected haze is usually less than 600 and more typically lessthan 550. The antiglare surface layer described herein generally has areflectance of less than 10%. However, the application of an antiglarecoating can reduce the transmission, transmitted haze, and clarity. Thetransmission is generally greater than 80%. Preferably, the transmissionis at least 85% and more preferably at least 90% or greater. Thetransmitted haze of the antiglare surface layer is typically less than30% and preferably less than 25%. Antiglare surface layers havingrelatively small surface structures can provide a transmitted haze ofabout 10%, whereas antiglare surface layers having larger surfacestructures can provide transmitted haze values of less than 10%. Forexample, the transmitted haze may be less than 8%, 7% or 6%. The clarityis at least 70% and preferably at least 80%. The test methods fordetermining such optical properties are described in the forthcomingexamples.

In combination with the optical properties just described, the antiglaresurface layer also exhibits high levels of durability. For example, thetouch screen has a scratch resistance as determined by the NanoscratchTest of at least 10 mN and preferably of at least 30 mN. Alternativelyor in addition thereto, the touch screen has a time to failure asdetermined by the Polishing Test of at least 2 hours for a 1 micrometerantiglare layer. Alternatively or in addition thereto, the touch screenhas Taber Abrasion Resistance of at least 100 cycles with CS-10Fabrasive wheels with a load of 500 g. The test methods for determiningsuch durability properties are described in the forthcoming examples.

As depicted in FIG. 2, the colloidal silica particles employed to formthe aggregates and thus the surface structures have a mean particle sizeof about 0.15 micrometers (150 nm). Typically, about 95% by weight ofthe colloidal silica particles employed to form the aggregates range insize from 0.005 micrometers to 0.30 micrometers. As depicted in FIG. 2,the starting colloidal silica particle distribution is substantiallyfree of particles having a particle size in excess of 0.30 micrometers.After the starting colloidal particles have been flocculated, as willsubsequently be described, the composition comprises a significantamount of aggregate particles having a size greater than 0.30micrometers. For example, at least 10 wt-% of the particles range insize from 0.30 micrometers to 2 micrometers (i.e. ten times that of themean particle size of the staring colloidal silica). An antiglaresurface layer at a magnification of 50×, which was prepared from acoating having such relatively small aggregates, is depicted in FIG. 3.It is evident from FIG. 3 that in at least some embodiments the surfacestructures are approximately evenly distributed.

The surface area of the surface structures relative to the total surfacearea of the antiglare layer is typically at least about 20%. The surfacearea of the surface structures is typically no greater than about 60%.In some embodiments, the surface area of the surface structures rangesfrom about 40% to about 50%.

The inorganic polymer preferably includes a source of silica that whensufficiently heated forms SiO₂.

The cured inorganic polymer matrix is preferably an organosilanesolution cured by means of heat. Organosilane solutions are known in theart and are typically derived from a “sol-gel” process.

Organosilanes can be represented by the following general formulaR_(n)SiX_(m)  (Formula I)

wherein R is an organofunctional group bounded to the silicon atom; X isa hydrolyzable group, such as a halogen or an alkoxy group, attached tothe silicon atom; n is 1 or 2; and m is 4−n.

A preferred organosilane solution is synthesized from the hydrolysis andcondensation of silicon alkoxides. (See for example C. J. Brinker and G.W. Scherer, “Sol-Gel Science”, Academic Press, 1990.) Such silanes havea molecular structure that is highly ordered. Preferred siliconalkoxides include for example tetraethoxysilane, methyltriethoxysilane,and mixtures thereof. Other suitable organosilanes are known in the art,such as described in EP 1 077 236.

A medium is typically used to dilute the organosilane as well as totransport the silane to the surface of the substrate being coated.Additionally, water reacts with organosilanes to form hydrolyzedproducts or silanols. Hydrolysis reactions between water andorganosilanes can be catalyzed in an acidic solution. Thus, astabilizing agent may be used so that the silanols are stable againstself-condensation reactions that may cause precipitation of the solutionif the solution is basic. The bond formed between the silanol and thesubstrate is accomplished through a cross condensation reaction. Thecross condensation reaction between a silanol and a molecule on thesubstrate is generally slow. This reaction can be accelerated byheating.

The antiglare surface layer is typically prepared from analcohol-containing coating composition. The aggregates can be formed byflocculating colloidal silica from a colloidal silica precursordispersed in an organosilane solution. Accordingly, the flocculatedparticles are prepared concurrently with the preparation of theorganosilane solution. Alternatively, however, the aggregates can beseparately formed, optionally separated from the non-flocculatedparticles, and then added to a stable organosilane solution.

The method of preparing the antiglare coating generally involvespreparing an organosilane solution (e.g. via sol-gel processes)including silica particle precursor and destabilizing the composition inorder to flocculate at least a portion of the silica particles. Variousmethods of flocculating colloidal silica particles are known such asdescribed in “One step antiglare sol-gel coatings for screens by sol-geltechniques”, Journal of Non-crystalline Solids 218 (1997) 163-168 andU.S. Pat. No. 5,998,013.

A preferred method of flocculation includes reacting colloidal silicawith at least one of several silicon alkoxide precursors to form asilane precursor and destabilizing the solution by addition of acid. Avariety of acids can usefully be employed. Typically inorganic acidssuch as hydrochloric acid, nitric acid, and the like are utilized. Thesolution may further comprise an adhesion promoter, sintering aid orflux to improve coating densification during the curing step. Sodiumacetate is a suitable additive. In the preparation thereof, the order ofaddition of these materials can vary. For example, the silicon alkoxideprecursors can be dispersed in an alcohol solution, followed by (e.g.sequential) addition of the sintering aid and acid. The colloidal silicasolution can then be combined with this mixture. This order of additionis preferred for obtaining relatively small aggregates. Alternatively,the silicon alkoxide precursors can first be combined with the colloidalsilica solution, followed by the (e.g. sequential) addition of the acid,sintering aid, and alcohol.

The antiglare coating composition can be prepared with a sol comprisingethyl silicate that is slowly added to a colloidal silica particleprecursor. A low level of particle flocculation growth will occur and afine textured antiglare finish can be produced.

The silica aggregates are formed from uniformly dispersed colloidalsilica in a solvent such as an alcohol. Examples of suitable solventsinclude 1-butanol, 2-propanol, ethanol, ethyl acetate, ethylene glycol,propylene glycol, acetone, and the like. The solvent may be used singlyor as a combination of two or more types. The percent solids in thecolloidal silica dispersion is generally about 5-50% (preferably, about15-30%), based on the total weight of the colloidal silica dispersion.Colloidal silica is commercially available from various suppliers.Nyacol Nanotechnolgies, Inc. Ashland, Mass. and Alfa Aesar, Ward Hill,Mass. both supply alcohol based sols having a mean particle size rangingfrom 20 to 50 nm. One preferred type of colloidal silica is a 30%solution of 100 nm colloidal silica in ethylene glycol, commerciallyavailable from Nanotechnologies, Inc. under the trade designation“Nyacol DP5540”.

Typically, small concentrations of colloidal silica are employed.Preferably the concentration of colloidal silica is less than 10 wt-% ofthe coating composition. More typically, the concentration of colloidalsilica is about 2 wt-%.

The coating compositions are generally stored in a closed container withstirring at room temperature for about 2 to 10 days prior to employingthe coating composition to coat a substrate. The aggregate-containingorganosilane coating solution is applied with a suitable method thatyields a thin substantially uniform layer. Precision dip coatingmachines are a preferred means of coating due to their smooth motion atprecise and accurate withdrawal speeds. When appropriately modified tothe proper rheology, the coating compositions described herein can beapplied by spray coating, meniscus coating, flow coating, screenprinting, or roll coating.

The coating compositions described herein exhibit sufficient adhesion toa wide variety of substrates. Glass and (e.g. ceramic) materials arepreferred substrates for illuminated display panel due to being bothtransparent and highly durable. The thickness of the glass substratetypically ranges from about 0.4 mm to about 4 mm. Soda lime glass andborosilicate glass are typically used for displays. The presentinvention is also suitable for improving the durability of antiglarecoatings on various plastic substrates, such as polycarbonate,polymethylmethacrylate, or cellulose acetate butyrate.

Alternatively, the transparent substrate may be a plastic film. Thethickness of the transparent substrate is generally at least 20micrometers and often at least 50 micrometers. Further, the transparentsubstrate is often less than 500 micrometers, and more often less than250 micrometers. The surface of the plastic film may be treated, wheredesirable, to increase adhesion of the antiglare layer. Examples of sucha treatment include formation of roughness on the surface by sandblasting or with a solvent, and oxidation of the surface by coronadischarge, treatment by chromic acid, treatment by flame, treatment byheated air, or irradiation by ultraviolet light in the presence ofozone.

For plastic substrates, an organosilane primer layer may be used toenhance the bonding between the (e.g. coated) substrate and theantiglare surface layer. Generally, an organosilane primer layercontains a very high concentration of hydroxyl groups and high angleSi—O—Si bonds. These are the bonding sites for the antiglare surfacelayer. Permanent bonding is formed by condensation reactions between theantiglare coating composition and the organosilane primer layer. TheSi—O—Si bonds are extremely durable.

For glass substrates, a silicon oxide layer is preferably disposedbetween the substrate and the antiglare layer. Such silicon oxide layeris surmised to improve adhesion of the antiglare layer to the substrate.Further, the presence of the silicon oxide layer can also improve thedurability of the antiglare layer and thus the article. For example, adisplay article having such a silicon oxide layer present can exhibit atleast a 25% increase in scratch resistance as determined by theNanoscratch Test. For example, scratch resistances of at least 20 mN, atleast 30 mN, or at least 40 mN have been obtained. Further, it has alsobeen found that a display article having such silicon oxide layerexhibits an increase in abrasion resistance in excess of 60% asdetermined by the Taber Abrasion Resistance test. The silicon oxidelayer may be applied by various methods, including sputtering,evaporation, chemical vapor depositions and sol-gel methods. U.S. Pat.Nos. 5,935,716; 6,106,892 and 6,248,397 disclose deposition of siliconoxide on glass.

After coating the antiglare coating composition, the coated substrate isthermally cured to drive off solvents and form a dense three-dimensionalfilm structure by thermally inducing self-condensation reactions withinthe coating material, which remove hydroxide groups from the remainingsilanol molecules and bond the structure together with the underlyingsubstrate. This can be accomplished in a batch process within anelectrical resistance element or gas fired oven with total cycle timesranging from 1.5 to 3 hours duration. Durability is generally enhancedas a result of full densification. Although complete densification ofthe coating composition typically occurs at about 800° C., the curingtemperature is chosen based on the heat resistance of the substrate.

A preferred method of curing an organosilane solution, particularly whenapplied to doped tin oxide coated glass, is described in U.S. Pat. No.6,406,758, incorporated herein by reference. Such method involves acombination of heat and infrared radiation in a chamber equipped withinfrared lamps or externally wound heater tubes emitting infraredradiation in the 2.5-6.0 micrometer wavelength spectrum. The use ofinfrared radiation introduces more energy into the coating while at thesame time reducing the thermal exposure of the glass substrate. In doingso, the curing temperature can be reduced to less than about 550° C.

The thickness of the cured antiglare land layer (i.e. at the locationsof the unstructured land) is typically at least 0.5 micrometers. Furtherthe thickness of the antiglare land layer is typically not greater than1.5 micrometers.

The antiglare layer may further comprise an antimicrobial layer disposedon the surface. A suitable antimicrobial layer is a liquid crystalsilane having the general formula:X₃Si(CH₂)_(p)Z  (Formula II)wherein p>1;X is selected from the group Cl, Br, alkoxy, hydroxyl radicals, andmixtures thereof, that are hydrolyzable to form a silanol; and

Z is a functional group selected from the group alkyl quaternaryammonium salts, alkyl sulfonium salts, alkyl phosphonium salts,substituted biphenyls, terphenyls, azoxybenzenes, cinnamates, pyridines,benzoates, and mixtures thereof.

Such liquid crystal silanes are commercially available from Dow Coming,Midland, Mich., under the trade designations “Dow Corning 5700” and “DowCorning 5772”. Such antimicrobial layers can provide additional scratchresistance.

Glare reducing transparent substrates (e.g. glass) are utilized in awide array of applications such as cathode ray tube screens or otherdisplay devices (monitors, televisions, liquid crystal displays, etc.);input or selection devices such as touch screens or input panels; glassenclosed displays (museums or other public displays); optical filters;picture frames; windows for architectural applications; glass componentsemployed in mirrors; solar collector cover plates; optical lensesutilized in eyewear and viewing devices; and windshields for vehicles.

Advantages of the invention are further illustrated by the followingexamples, but the particular materials and amounts thereof recited inthe examples, as well as other conditions and details, should not beconstrued to unduly limit the invention. All percentages and ratiosherein are by weight unless otherwise specified.

EXAMPLES Test Methods

Polishing Wear Test

Coated glass was cut to 3 cm×4 cm rectangular samples. Edges and comerswere sanded to minimize breakage. The samples were then washedthoroughly with water to remove particulate, then with isopropanol-basedglass cleaner, and then soaked in acetone for 1 minute in order toremove residual water. The samples were then wiped clean using alint-free cloth, allowed to air dry for 30 minutes, and then weighed(Mettler Toledo International Inc., Columbus, Ohio, P.N. AX205).

The samples were polished on the coated side of the glass for 30 minutesat 100% amplitude in 180 g sample holders. The polishing instrument wasa Buehler VIBROMET 2 Polisher (Buehler LTD, Lake Bluff, Ill., P.N.67-1635). The polishing cloth was Buehler Microcloth (Buehler LTD, LakeBluff, Ill., P.N. 40-7222). The polishing media was a slurry of 50 g of1.0 micrometer alumina powder in 1000 ml of deionized water (MICROPOLISHII, Buehler LTD, Lake Bluff, Ill., P.N. 40-6321-080). After 30 minutesof polishing at 100% amplitude, the samples were removed, washed inwater, then isopropanol-based cleaner, and then acetone. The sampleswere then wiped with a lint-free cloth, air-dried for 30 minutes, andthen reweighed.

After 120 minutes of polishing, the samples were left to polish untilcontinuity could be made between two points at the surface. Using amultimeter, resistance was measured at two points 2 cm apart in thecenter of each coated glass sample.

Wear rate was calculated as the total weight lost over the course of 120minutes of polishing time. Time to failure was the time at whichcontinuity was made between two points 2 cm apart.

Nanoscratch

Nanoscratch resistance was measured using a Nanoscratch tester (CSMInstruments, Needham, Mass.). Testing was performed using a progressivescratch load increasing from 2 mN to 100 mN. A 2 micrometer sphericaldiamond indenter was used as the probe.

Taber Abrasion Resistance

A Taber Abraser 5130 (Taber Industries, North Tonawanda, N.Y.,) was usedto abrade the samples. Two CS-10F abrasive wheels (Taber Industries,North Tonawanda, N.Y.) were used that consist of Al₂O₃ particlesembedded in rubber. Each wheel was weighted with 500 g and resurfacedwith 150 grit sandpaper (Taber Industries, North Tonawanda, N.Y., P.N.ST-11). Abrasion was conducted for 100 cycles on the samples with thewheels being resurfaced for another 25 cycles on the sandpaper.Resistance was measured between the printed center point and surroundingring before abrasion and after each set of 100 cycles.

Glass was printed with a thick film of silver paste in a test patternconsisting of two concentric rings surrounding the wear region createdby the Abraser. The glass samples were then coated, fired, and cut into5 inch (12.5 cm) squares.

Failure is defined as a 25% increase in electrical resistance.

Transmission

The transmittance of the article was measured using a BYK GardnerHaze-Guard plus.

Transmitted Haze

The transmitted haze of the article was measured using a BYK GardnerHaze-Guard plus.

Clarity

Clarity of the optical articles was measured using a BYK GardnerHaze-Guard plus. The sample was positioned perpendicularly to the lightsource path. Clarity is calculated from the values of unscatteredtransmitted light and light scattered less than 2.5° from the incidentbeam, as measured by circle and ring photo detectors.

Reflected Haze

Reflected haze was measured with a BYK-Gardner Haze-Gloss Meter.

Reflectance

Reflectance was measured using a BYK-Gardner TCS II at 550 nm withspecular reflection included.

Example 1

A 3 kg batch of an antiglare coating composition was prepared asfollows: In a vessel equipped with a stirring paddle, 34.06 weight %tetraethoxysilane (Dynasil A, Sivento Corp.) was added to 19.45%methyltriethoxysilane (Dynasilan MTES, Sivento Corp.). Stirring was thenstarted and continued throughout the mixing process. 1.83% ethyl alcoholwas then added followed by 12.73% of 2-propanol. After 5 minutes, amixture of 11.31% deionized water and 0.11% sodium acetate trihydratewas added to the above. After 10 minutes, 0.11% concentrated nitric acidwas added to the stirring mixture. After a 2-hour reaction time, 13.65%2-propanol was added. The resultant partially hydrolyzed ethyl silicatesolution was then allowed to age for a period of 2 days. After the agingperiod, 6.75% DP5540 (Nyacol Corp.) (30% 100 nm colloidal silicadispersed in ethylene glycol) was added at a flow rate of 15 ml/minute.The completed coating composition was kept stored under constantstirring. Before use, the coating composition was aged for 2 days in aclosed container at room temperature under constant stirring. Thecoating composition was then gravity filtered through a 10 μm meshfilter prior to coating.

Example 1 was coated onto two different substrates. The first substratewas soda lime glass. The second substrate was a display panel for atouch screen that was comprised of clean, soda lime glass plates with afluorine-doped tin oxide transparent conductive coating disposed on oneside, a thin (i.e. less than 500 angstroms) layer of silicon oxidedisposed on the conductive coating, and a thick film circuit, asdescribed in U.S. Pat. No. 6,727,895, further disposed upon the siliconoxide layer. During heating the thick film circuit penetrates thesilicon oxide layer such that electrical contact is made with theunderlying conductive layer.

The coating was applied to either the glass or the silicon oxide layerof the display panel with a precision dip coating machine at awithdrawal speed set at 0.13 inches (0.33 cm) per second. A suitableprecision dip coating machine is available from Chemat Technology,Northridge Inc, Calif. under the trade designation “Dip-Master 200”.After the dip coating cycle was complete, a one-minute drying time wasallowed to elapse before the coated substrates were removed from the dipcoating machine enclosure. The coated substrates were then cured in aninfrared curing oven as disclosed in U.S. Pat. No. 6,406,758.

An anti-scratch and anti-microbial treatment was then applied to thecoated substrates by applying a homeotropic liquid crystal silanesolution to the substrates and curing as disclosed in U.S. Pat. Nos6,504,582 and 6,504,583. Although the exemplified constructions includedsuch liquid crystal silane surface layer, similar results were obtainedwithout this layer (i.e. antiglare layer present on the surface).

The antiglare surface layer was viewed with a microscope (5 OX). Theantiglare surface layer of Example 1 is depicted in FIG. 3. It was alsoconfirmed by optical microscopy that the surface structures werecomposed of discrete silica particles and are therefor true aggregates.

The surface area fraction of the surface structures was determined to be46% for Example 1 as determined using optical microscopy and imageanalysis Software (Image Pro Plus 4, Media Cybernetics).

The optical properties of the coated substrates in comparison to acontrol lacking the antiglare layer were evaluated. Table 1 as followsreports the average value for at least 3 samples and the standarddeviation: TABLE 1 Reflectance Reflected Coating Composition (Substrate)Transmission (%) Haze (%) Clarity (%) at 550 nm (%) Haze Control - glasswith transparent 86.5 ± 0.5% 0.5 ± 0.1% 100% 11.4 ± 0.5%  37 ± 3conductive coatings but no antiglare coating Example 1 91.5 ± 0.5  10 ±5 95 ± 3  6.5 ± 0.5 260 ± 30 (glass with transparent conductive coating)

The durability properties of the coated substrates were evaluated. Table2 as follows reports the average value for at least 3 samples and thestandard deviation: TABLE 2 Coating Polishing Wear Nano Scratch NanoScratch (through Composition Test Time to (through top top layer and(Substrate) Failure (min) layer only) silicon oxide layer Example 1 369± 38 44 ± 8 mN 60 ± mN glass with transparent conductive coating

The abrasion resistance of Example 1 was determined with and without asilicon oxide layer using a Taber Abrader. With the silicon oxide layerpresent the article was able to withstand 500 cycles before failurewhereas without the silicon oxide layer failure occurred at 300 cycles.

1. A touch screen comprising a glass substrate, an active element fordetecting a touch on the touch screen, and an antiglare layer whereinthe antiglare layer comprises aggregate silica particles in a curedinorganic polymer matrix wherein the aggregates form surface structuresranging in size from 0.1 micrometers to 2 micrometers.
 2. The touchscreen of claim 1 wherein the touch screen has a reflected haze of atleast
 150. 3. The touch screen of claim 1 wherein the touch screen has areflectance of less than 10%.
 4. The touch screen of claim 1 wherein thetouch screen has a transmission of at least 80%.
 5. The touch screen ofclaim 1 wherein the touch screen has a scratch resistance as determinedby the Nanoscratch Test of at least 10 mN.
 6. The touch screen of claim1 wherein the touch screen has a Taber Abrasion Resistance test of atleast 100 cycles.
 7. The touch screen of claim 1 wherein the touchscreen has a time to failure as determined by the Polishing Test of atleast 2 hours for a 1 micrometer antiglare layer.
 8. The touch screen ofclaim 1 wherein the silica particles have a mean particle size rangingfrom about 0.05 micrometers to about 0.15 micrometers.
 9. The touchscreen of claim 1 wherein the surface structures have a dimension of atleast 0.20 micrometers.
 10. The touch screen of claim 1 wherein thesurface structures have a dimension of at least 0.30 micrometers. 11.The touch screen of claim 1 wherein the cured inorganic polymer matrixis derived from an organosilane.
 12. The touch screen of claim 11wherein the cured inorganic polymer matrix is derived from a siliconalkoxide.
 13. The touch screen of claim 11 wherein the curedorganosilane is derived from a sol-gel process.
 14. The touch screen ofclaim 1 wherein the surface layer has a total surface area and thesurface structures comprise at least 20% of the total surface area. 15.The touch screen of claim 1 wherein the surface layer has a totalsurface area and the surface structures comprise at least 30% of thetotal surface area.
 16. The touch screen of claim 1 wherein the surfacelayer has a total surface area and the surface structures comprise atleast 40% of the total surface area.
 17. The touch screen of claim 1,further comprising a silicon oxide layer disposed between thetransparent conductive layer and the antiglare layer.
 18. The touchscreen of claim 1, wherein the active element comprises a transparentconductive layer disposed between the glass substrate and the antiglarelayer.
 19. The touch screen of claim 18, wherein the transparentconductive layer comprises a transparent conductive oxide.
 20. The touchscreen of claim 1 further comprising a liquid crystal silane surfacelayer.
 21. An article comprising an antiglare layer wherein theantiglare layer comprises aggregate silica particles in a curedinorganic polymer matrix wherein the aggregate silica particles formsurface structures ranging in size from 0.2 micrometers to 2micrometers.
 22. The article of claim 21 wherein the article is adisplay panel.
 23. The article of claim 21 wherein the article isselected from the group comprising computer monitors, televisionscreens, optical filters, picture frames, windows, mirrors, solarcollector cover plates, optical lenses, and windshields for vehicles.24. A coating composition comprising an organosilane and flocculatedsilica particles ranging in size from 0.2 micrometers to 2 micrometers.25. The coating composition of claim 24 wherein the silica particles arepresent in a concentration of less than 10 wt-%.
 26. A method of makingan antiglare article comprising: providing a transparent substrate;coating the substrate with the coating composition of claim 24; andheating the coating composition.
 27. The method of claim 26 wherein thesubstrate is selected from glass, polycarbonate, polymethylmethacrylate,and cellulose acetate butyrate.
 28. A method of making an antiglarecoating composition comprising: providing an inorganic polymer precursorand colloidal silica particles having a mean particle size ranging from0.05 micrometers to 0.15 micrometers; and forming an inorganic polymersolution concurrently with flocculating colloidal silica aggregates. 29.The method of claim 28 wherein the method comprises the addition ofsodium acetate.